Browsing by Author "Moradi, Shahpoor"

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    On the deployment and testing of a quantum ground station for satellite Quantum Key Distribution
    (2024-08-19) Yastremski, Mathew A.; Oblak, Daniel; Simon, Christoph; Taylor, Matthew; Moradi, Shahpoor
    Satellite-based Quantum Key Distribution (QKD) uses the fundamental properties of quantum mechanics to offer unparalleled security against eavesdroppers with the ability to scale quantum networks globally. Its use of quantum mechanics to protect information makes QKD the best choice currently for next generation secure communication systems. The implementation of satellite-based QKD still has many challenges to overcome before it becomes a widely used method of secure communication. This thesis discusses some fundamentals of classic cryptography and why moving towards quantum-based security protocols is necessary. We introduce a range of considerations for establishing a reliable long-distance free-space satellite optical link, thus allowing QKD to occur. Since a substantial amount of research has already been conducted on optical fiber communication for terrestrial links, our focus is specifically directed towards free space quantum links. While we discuss the protocols used with current experiments, we further focus the discussion around how background noise present in these free-space satellite channels can contribute to lower Signal-to-Noise Ratios (SNRs). Additionally, we experimentally measure background noise and light pollution expected at three quantum ground station locations: The University of Calgary, Rothney Astrophysical Observatory, and the University of Waterloo. The experimental measurements were taken at periods during which high atmospheric background noise was predicted. These measurements aim to show the anticipated background light during a downlink QKD experiment, when the ground station is used as a receiver and the satellite as a transmitter of quantum signals. To measure the expected background noise of an uplink QKD experiment, one for which the satellite is the receiver, we use the Visible Infrared Imaging Radiometer Suite Day-Night Band (VIIRS-DNB) instrument onboard the Suomi National Polar-orbiting Partnership (NPP) satellite. This satellite gives a spectra for a requested day in the 500 nm to 900 nm bandwidth. As many QKD experiments of interest fall within the upper range of this bandwidth, this satellite data is an excellent candidate for our analysis. In this thesis we show a comprehensive analysis of background noise and help find the background noise limit for future satellite-based QKD experiments, such as the upcoming Quantum Encryption and Science Satellite (QEYSSat).
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    Scattering of Seismic Waves from Arbitrary Viscoelastic-Isotropic and Anisotropic Structures with Applications to Data Modelling, FWI Sensitivities and Linearized AVO-AVAz Analysis
    (2017) Moradi, Shahpoor; Innanen, Kristopher A.; Liu, Qinya; Lamoureux, Michael; Krebes, Edward S.; Lines, Laurence R.
    It is acknowledged that Full Waveform Inversion (FWI) techniques are sensitive to the set of model parameters that we choose for the minimization procedure. This model parametrization and sensitivity analysis for FWI has been extensively studied for acoustic and isotropic-elastic media. In order to obtain an accurate image of subsurface earth, it is necessary to include both anisotropy and attenuation in inversion procedures as subsurface materials are far from being isotropic or elastic. In this thesis, we formulate the sensitivity analysis for FWI in viscoelastic-isotropic/anisotropic media. To develop such analysis, we construct a framework based on the first order perturbation theory called the Born approximation to find the sensitivity of the FWI to isotropic, anelastic and anisotropic parameters. Sensitivities are, essentially, radiation patterns induced by scattering of the seismic waves from inclusions in medium properties in an isotropic background. Most importantly, we investigate the effect of the inhomogeneity angle which is unique to viscoelastic waves, on these radiation patterns (scattering potentials) and also on amplitude-variation-with-offset or azimuth (AVO/AVAz) analysis. By decomposition of the scattering potentials into isotropic, viscoelastic and anisotropic components, we specify the effects of anelasticity, inhomogeneity of wave and anisotropy on radiation patterns and the linearized AVO/AVAz equations. Moreover, we show how the obtained scattering potentials reduce to the linearized AVO/AVAz equations without using the solution of Zoeppritz equations. This analysis is the starting point for any FWI strategy in a complex media exhibiting both attenuation and anisotropy, as the scattering potentials that we obtained can be effectively implemented to choose a suitable model parametrization.